B) L rearing tank in oi)eration, closo viev;. Note the 

 Inrvae o.nd also the over-flov/,^ 



• Plr.to II - Bcitteries of fcvro rerfring ' 

 troughs supplied by n 

 single source of vmter* 



a) Upper trough uncove-red to show the partitions and 

 corresponding outlets. Note at the nearest end 

 the rectangular receptacle for collecting the larvae* 



B) Trough in operation Virith its cover in order to keep 

 the fenales in darlcness. The v/ater enters at the 

 . renote end of the upper trough and flcv/s in the 

 center up to the receiving collector v.dth nesh botton 

 anr' fr.-^:a there into the lovrer trough T/hich is shovm 

 in V. reverse sense* 



Table IV ;;ives the allotment of the groups of larvae used in 

 rearing. The analysis of this Table shov;s that the groups of basins 

 of the type in use at Boothbay Harbor are nore homogeneous v.dth 

 regard to the age of the individuals than those of the oval tanks* 

 In the latter, the first larvae ere already some days old at the 

 arrival of the latest* ITe have ascertained that the recently hatched 

 larvae are voracious during the first days and devoured their older 

 congeners", vreahened by the physiological nodificatiox:s Trhich accompany 

 or precede the moult ing»_ 



The honcg'eneity of the groups of larvae is an essential factor to 

 assiu'e a. good percentage survival to the 4th stage. This fact shows 

 itself clearly in Table V in v/hich we have set up the comparison of 

 the survival in the oval tan±s and. in those of the "Boothbay Harbor" 

 type. 



To conduct the homogeneous rearing in the oval tanks, it is 

 important to have some hundreds of egg-bearing f enables in an 

 enclosiore in order to gather in 24 hours the quantity of young larvae 

 necessary to form a homogeneous group filling up a tank. 



Tables VI, VII, VIII, LX, X shov; the detailed results of otir 

 observations for each rearing group in the oval tanlcs. In the case 

 where tvro broods havinjg attained approxianritely to the so^iSb stage v/ere 

 united together, the results figure in the same Table. The data for 

 the observations in "Boothbay Harbor" type basins are shown in 

 Tables XI, XII, XIII, 



27 



